Subject: [PATCH 1/2] net: Implement SO_PEERCGROUP

From: Vivek Goyal <[email-masked]>
Date: Tue, 15 Apr 2014 17:15:45 -0400

Implement SO_PEERCGROUP along the lines of SO_PEERCRED. This returns the
cgroup of first mounted hierarchy of the task. For the case of client,
it represents the cgroup of client at the time of opening the connection.
After that client cgroup might change.

This works only for unix stream sockets.

Signed-off-by: Vivek Goyal <[email-masked]>
---
 arch/alpha/include/uapi/asm/socket.h   |  1 +
 arch/avr32/include/uapi/asm/socket.h   |  1 +
 arch/cris/include/uapi/asm/socket.h    |  2 ++
 arch/frv/include/uapi/asm/socket.h     |  1 +
 arch/ia64/include/uapi/asm/socket.h    |  2 ++
 arch/m32r/include/uapi/asm/socket.h    |  1 +
 arch/mips/include/uapi/asm/socket.h    |  1 +
 arch/mn10300/include/uapi/asm/socket.h |  1 +
 arch/parisc/include/uapi/asm/socket.h  |  1 +
 arch/powerpc/include/uapi/asm/socket.h |  1 +
 arch/s390/include/uapi/asm/socket.h    |  1 +
 arch/sparc/include/uapi/asm/socket.h   |  2 ++
 arch/xtensa/include/uapi/asm/socket.h  |  1 +
 include/net/sock.h                     |  2 ++
 include/uapi/asm-generic/socket.h      |  2 ++
 net/core/sock.c                        | 19 ++++++++++
 net/unix/af_unix.c                     | 66 +++++++++++++++++++++++++++++++++-
 17 files changed, 104 insertions(+), 1 deletion(-)

diff --git a/arch/alpha/include/uapi/asm/socket.h b/arch/alpha/include/uapi/asm/socket.h
index 3de1394..7178353 100644
--- a/arch/alpha/include/uapi/asm/socket.h
+++ b/arch/alpha/include/uapi/asm/socket.h
@@ -87,4 +87,5 @@
 
 #define SO_BPF_EXTENSIONS	48
 
+#define SO_PEERCGROUP		49
 #endif /* _UAPI_ASM_SOCKET_H */
diff --git a/arch/avr32/include/uapi/asm/socket.h b/arch/avr32/include/uapi/asm/socket.h
index 6e6cd15..486212b 100644
--- a/arch/avr32/include/uapi/asm/socket.h
+++ b/arch/avr32/include/uapi/asm/socket.h
@@ -80,4 +80,5 @@
 
 #define SO_BPF_EXTENSIONS	48
 
+#define SO_PEERCGROUP		49
 #endif /* _UAPI__ASM_AVR32_SOCKET_H */
diff --git a/arch/cris/include/uapi/asm/socket.h b/arch/cris/include/uapi/asm/socket.h
index ed94e5e..89a09e3 100644
--- a/arch/cris/include/uapi/asm/socket.h
+++ b/arch/cris/include/uapi/asm/socket.h
@@ -82,6 +82,8 @@
 
 #define SO_BPF_EXTENSIONS	48
 
+#define SO_PEERCGROUP		49
+
 #endif /* _ASM_SOCKET_H */

diff --git a/arch/frv/include/uapi/asm/socket.h b/arch/frv/include/uapi/asm/socket.h
index ca2c6e6..c4d90bc 100644
--- a/arch/frv/include/uapi/asm/socket.h
+++ b/arch/frv/include/uapi/asm/socket.h
@@ -80,5 +80,6 @@
 
 #define SO_BPF_EXTENSIONS	48
 
+#define SO_PEERCGROUP		49
 #endif /* _ASM_SOCKET_H */
 
diff --git a/arch/ia64/include/uapi/asm/socket.h b/arch/ia64/include/uapi/asm/socket.h
index a1b49ba..62c196d 100644
--- a/arch/ia64/include/uapi/asm/socket.h
+++ b/arch/ia64/include/uapi/asm/socket.h
@@ -89,4 +89,6 @@
 
 #define SO_BPF_EXTENSIONS	48
 
+#define SO_PEERCGROUP		49
+
 #endif /* _ASM_IA64_SOCKET_H */
diff --git a/arch/m32r/include/uapi/asm/socket.h b/arch/m32r/include/uapi/asm/socket.h
index 6c9a24b..6e04a7d 100644
--- a/arch/m32r/include/uapi/asm/socket.h
+++ b/arch/m32r/include/uapi/asm/socket.h
@@ -80,4 +80,5 @@
 
 #define SO_BPF_EXTENSIONS	48
 
+#define SO_PEERCGROUP		49
 #endif /* _ASM_M32R_SOCKET_H */
diff --git a/arch/mips/include/uapi/asm/socket.h b/arch/mips/include/uapi/asm/socket.h
index a14baa2..cfbd84b 100644
--- a/arch/mips/include/uapi/asm/socket.h
+++ b/arch/mips/include/uapi/asm/socket.h
@@ -98,4 +98,5 @@
 
 #define SO_BPF_EXTENSIONS	48
 
+#define SO_PEERCGROUP		49
 #endif /* _UAPI_ASM_SOCKET_H */
diff --git a/arch/mn10300/include/uapi/asm/socket.h b/arch/mn10300/include/uapi/asm/socket.h
index 6aa3ce1..73467fe 100644
--- a/arch/mn10300/include/uapi/asm/socket.h
+++ b/arch/mn10300/include/uapi/asm/socket.h
@@ -80,4 +80,5 @@
 
 #define SO_BPF_EXTENSIONS	48
 
+#define SO_PEERCGROUP		49
 #endif /* _ASM_SOCKET_H */
diff --git a/arch/parisc/include/uapi/asm/socket.h b/arch/parisc/include/uapi/asm/socket.h
index fe35cea..24d8913 100644
--- a/arch/parisc/include/uapi/asm/socket.h
+++ b/arch/parisc/include/uapi/asm/socket.h
@@ -79,4 +79,5 @@
 
 #define SO_BPF_EXTENSIONS	0x4029
 
+#define SO_PEERCGROUP           0x402a
 #endif /* _UAPI_ASM_SOCKET_H */
diff --git a/arch/powerpc/include/uapi/asm/socket.h b/arch/powerpc/include/uapi/asm/socket.h
index a9c3e2e..50106be 100644
--- a/arch/powerpc/include/uapi/asm/socket.h
+++ b/arch/powerpc/include/uapi/asm/socket.h
@@ -87,4 +87,5 @@
 
 #define SO_BPF_EXTENSIONS	48
 
+#define SO_PEERCGROUP		49
 #endif	/* _ASM_POWERPC_SOCKET_H */
diff --git a/arch/s390/include/uapi/asm/socket.h b/arch/s390/include/uapi/asm/socket.h
index e031332..4ae2f3c 100644
--- a/arch/s390/include/uapi/asm/socket.h
+++ b/arch/s390/include/uapi/asm/socket.h
@@ -86,4 +86,5 @@
 
 #define SO_BPF_EXTENSIONS	48
 
+#define SO_PEERCGROUP		49
 #endif /* _ASM_SOCKET_H */
diff --git a/arch/sparc/include/uapi/asm/socket.h b/arch/sparc/include/uapi/asm/socket.h
index 54d9608..1056168 100644
--- a/arch/sparc/include/uapi/asm/socket.h
+++ b/arch/sparc/include/uapi/asm/socket.h
@@ -76,6 +76,8 @@
 
 #define SO_BPF_EXTENSIONS	0x0032
 
+#define SO_PEERCGROUP           0x0033
+
 /* Security levels - as per NRL IPv6 - don't actually do anything */
 #define SO_SECURITY_AUTHENTICATION		0x5001
 #define SO_SECURITY_ENCRYPTION_TRANSPORT	0x5002
diff --git a/arch/xtensa/include/uapi/asm/socket.h b/arch/xtensa/include/uapi/asm/socket.h
index 39acec0..947bc6e 100644
--- a/arch/xtensa/include/uapi/asm/socket.h
+++ b/arch/xtensa/include/uapi/asm/socket.h
@@ -91,4 +91,5 @@
 
 #define SO_BPF_EXTENSIONS	48
 
+#define SO_PEERCGROUP		49
 #endif	/* _XTENSA_SOCKET_H */
diff --git a/include/net/sock.h b/include/net/sock.h
index 8338a14..baab092 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -291,6 +291,7 @@ struct cg_proto;
   *	@sk_error_report: callback to indicate errors (e.g. %MSG_ERRQUEUE)
   *	@sk_backlog_rcv: callback to process the backlog
   *	@sk_destruct: called at sock freeing time, i.e. when all refcnt == 0
+  *	@sk_peer_cgroup: client cgroup path of peer socket.
  */
 struct sock {
 	/*
@@ -424,6 +425,7 @@ struct sock {
 	int			(*sk_backlog_rcv)(struct sock *sk,
 						  struct sk_buff *skb);
 	void                    (*sk_destruct)(struct sock *sk);
+	char			*sk_peer_cgroup;
 };
 
 #define __sk_user_data(sk) ((*((void __rcu **)&(sk)->sk_user_data)))
diff --git a/include/uapi/asm-generic/socket.h b/include/uapi/asm-generic/socket.h
index ea0796b..e86be5b 100644
--- a/include/uapi/asm-generic/socket.h
+++ b/include/uapi/asm-generic/socket.h
@@ -82,4 +82,6 @@
 
 #define SO_BPF_EXTENSIONS	48
 
+#define SO_PEERCGROUP		49
+
 #endif /* __ASM_GENERIC_SOCKET_H */
diff --git a/net/core/sock.c b/net/core/sock.c
index b4fff00..2926774 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1185,6 +1185,24 @@ int sock_getsockopt(struct socket *sock, int level, int optname,
 		v.val = sk->sk_max_pacing_rate;
 		break;
 
+	case SO_PEERCGROUP:
+	{
+		int cgroup_path_len;
+
+		if (!sk->sk_peer_cgroup) {
+			len = 0;
+			goto lenout;
+		}
+
+		cgroup_path_len = strlen(sk->sk_peer_cgroup) + 1;
+
+		if (len > cgroup_path_len)
+			len = cgroup_path_len;
+		if (copy_to_user(optval, sk->sk_peer_cgroup, len))
+			return -EFAULT;
+		goto lenout;
+	}
+
 	default:
 		return -ENOPROTOOPT;
 	}
@@ -1378,6 +1396,7 @@ static void __sk_free(struct sock *sk)
 		put_cred(sk->sk_peer_cred);
 	put_pid(sk->sk_peer_pid);
 	put_net(sock_net(sk));
+	kfree(sk->sk_peer_cgroup);
 	sk_prot_free(sk->sk_prot_creator, sk);
 }
 
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index bb7e8ba..892ea50 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -473,6 +473,46 @@ static void copy_peercred(struct sock *sk, struct sock *peersk)
 	sk->sk_peer_cred = get_cred(peersk->sk_peer_cred);
 }
 
+static int sk_alloc_cgroup_path(struct sock *sk)
+{
+#ifdef CONFIG_CGROUPS
+	if (sk->sk_peer_cgroup)
+		return 0;
+
+	sk->sk_peer_cgroup = kzalloc(PATH_MAX, GFP_KERNEL);
+	if (!sk->sk_peer_cgroup)
+		return -ENOMEM;
+
+#endif
+	return 0;
+}
+
+static int init_peercgroup(struct sock *sk)
+{
+#ifdef CONFIG_CGROUPS
+	int ret;
+	char *path;
+
+	ret = sk_alloc_cgroup_path(sk);
+	if (ret)
+		return ret;
+
+	path = task_cgroup_path(current, sk->sk_peer_cgroup, PATH_MAX);
+	if (!path)
+		return -ENAMETOOLONG;
+
+	if (path != sk->sk_peer_cgroup)
+		memmove(sk->sk_peer_cgroup, path, strlen(path) + 1);
+#endif
+	return 0;
+}
+
+static void copy_peercgroup(struct sock *sk, struct sock *peersk)
+{
+	if (sk->sk_peer_cgroup)
+		strncpy(sk->sk_peer_cgroup, peersk->sk_peer_cgroup, PATH_MAX);
+}
+
 static int unix_listen(struct socket *sock, int backlog)
 {
 	int err;
@@ -486,6 +526,12 @@ static int unix_listen(struct socket *sock, int backlog)
 	err = -EINVAL;
 	if (!u->addr)
 		goto out;	/* No listens on an unbound socket */
+
+	err = init_peercgroup(sk);
+	if (err)
+		goto out;
+
+	err = -EINVAL;
 	unix_state_lock(sk);
 	if (sk->sk_state != TCP_CLOSE && sk->sk_state != TCP_LISTEN)
 		goto out_unlock;
@@ -1097,6 +1143,16 @@ static int unix_stream_connect(struct socket *sock, struct sockaddr *uaddr,
 	if (newsk == NULL)
 		goto out;
 
+	err = init_peercgroup(newsk);
+	if (err)
+		goto out;
+
+	err = sk_alloc_cgroup_path(sk);
+	if (err)
+		goto out;
+
+	err = -ENOMEM;
+
 	/* Allocate skb for sending to listening sock */
 	skb = sock_wmalloc(newsk, 1, 0, GFP_KERNEL);
 	if (skb == NULL)
@@ -1202,6 +1258,7 @@ restart:
 
 	/* Set credentials */
 	copy_peercred(sk, other);
+	copy_peercgroup(sk, other);
 
 	sock->state	= SS_CONNECTED;
 	sk->sk_state	= TCP_ESTABLISHED;
@@ -1237,6 +1294,14 @@ out:
 static int unix_socketpair(struct socket *socka, struct socket *sockb)
 {
 	struct sock *ska = socka->sk, *skb = sockb->sk;
+	int ret = 0;
+
+	ret = init_peercgroup(ska);
+	if (ret)
+		return ret;
+	ret = init_peercgroup(skb);
+	if (ret)
+		return ret;
 
 	/* Join our sockets back to back */
 	sock_hold(ska);
@@ -1245,7 +1310,6 @@ static int unix_socketpair(struct socket *socka, struct socket *sockb)
 	unix_peer(skb) = ska;
 	init_peercred(ska);
 	init_peercred(skb);
-
 	if (ska->sk_type != SOCK_DGRAM) {
 		ska->sk_state = TCP_ESTABLISHED;
 		skb->sk_state = TCP_ESTABLISHED;
-- 
1.9.0